Plant roots release as exudates different organic compounds including low molecular organic acids,phytosiderophores,flavonoids compounds/phenolic compounds and enzymes,etc.They induce changes in the chemical,physical and biologic characteristics of rhizosphere.These changes mobilize micronutrients like iron ,manganese etc.What are the significant contributions of these organic compounds singly and in combination in mobilizing micronutrients in soil ?
The rood exudates having low molecular organic acids, which make the complexes with metal ions and enhanced the micronutrient uptake in plants.
Please refer: Rhizosphere Chemistry (2013). In: The Role of Plant Roots in Crop Production written by Nand Kumar Fageria published by CRC press
Dear colleagues ,Can we get some quantification of the relative contribution of organic acids, siderophores ,flavonoids,enzymes in solubilization of micronutrients in soil ? Also, is there some complementary role among these?For cationic micronutrients like Fe, Mn, Zn in neutral and alkaline pH range , these organic compounds may have greater role in their solubilization in rhizosphere soil.
Respected Sir,
Plants develop several methods of adaptation in response to nutrient availability in soil. If the necessary nutrients are available easily plants grow normally. But such ideal soils are rarity in present day arable lands.
The first adaptive change plant does to nutrient limitation is alter its root structure such that it can forage nutrients from large area.
Then depending upon the nutrient that is limiting it will alter its metabolism and secrete exudates that can selectively aid in improved absorption of the limiting nutrient. Ex., if iron or zinc is limiting it will produce phytosiderophores for their chelation and absorption, or organic acids to improve uptake of phosphorus, copper and manganese etc. Plant roots also produce reactive oxygen and proteases that help them absorb nitrogen from organic sources (white et al., AoB Plants, 2015, DOI: 10.1093/aobpla/plu093).
In addition to all these methods, plants also recruit beneficial bacteria and fungi in their rhizosphere and endosphere compartment that help them to absorb critical nutrients for their growth.
For information on root exudate quantification you can look into the work of Harsh Bais for their excellent research in this area(http://canr.udel.edu/faculty/harsh-bais/). The paper of Dakora and Philips Plant and Soil 245: 35–47, 2002 also would be helpful.
Thanks
Dear Dr .Gopal, I appreciate your good reply and referring to good work of Dr.Harsh Bais . We have been studying the role of pH, red-ox reactions, proton release from roots,CO2 production(from respiration and organic matter decomposition),root exudate derived organic compounds and associated microbial activities .Lot of new and exciting information has been generated and excellent reviews are now available. But the main problem is these studies have been conducted individually by soil scientists,plant physiologists and microbiologists .In view of limitations of moisture ,temperature fluctuations, oxygen and CO2 supply (in view of changing climate),we need very good team work with participation of soil scientists/agronomists, plant physiologists/ geneticist and microbiologist/biotechnologist to study these processes in rhizosphere and do quantification.This will help to synthesize the information and also develop models also.Colleagues can inform if any teams are working in this line.
This weeks Nature (vol 525, issue 7569) says interdisciplinary research is the need of the hour to solve serious problems faced by earth. Interestingly, surprisingly, India appears to be leading the publications percentage in interdisciplinary research. Agriculture research must take a leaf out it to synthesize comprehensive information and develop models as you rightly mention....
I thank all the participants for excellent discussion and new ideas generated on the subject.
I thank all the participants for excellent discussion and new ideas generated on the subject.
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